HP LP 2456 monitor wont turn on

I turned off my PC and then 10 mins later turned it back on but my screen wont turn on and whenever i press any of the buttons on the front it says monitor going to sleep and the led stays orange until i touch a button then it turns green and then it turns orange again and the screen stays black pls help me my monitor is a HP LP 2456 and im writing this from another computer and i have replugged the cables and whenever i take one of the video cables out it says please check the video cable